/**  
 * @date 2023-11-24 
 * @author Zhang Yu
 */
package com.jwt.shiro.demo.filter;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;

import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.shiro.web.filter.authc.BasicHttpAuthenticationFilter;
import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.RequestMethod;

import com.jwt.shiro.demo.shiro.JWTToken;

/**  
 * @description: TODO
 */
public class JWTFilter extends BasicHttpAuthenticationFilter {

	/**
	 * 如果带有 token，则对 token 进行检查，否则直接通过
	 */
	@Override
	protected boolean isAccessAllowed(ServletRequest request, ServletResponse response, Object mappedValue) {
        //判断请求的请求头是否带上 "Token"
		if (isLoginAttempt(request, response)) {
			try {
	            //如果存在，则进入 executeLogin 方法执行登入，检查 token 是否正确
				executeLogin(request, response);
				return true;
			} catch (Exception e) {
				responseError(response, e.getMessage());
			}
		}
        //如果请求头不存在 Token，则可能是执行登陆操作或者是游客状态访问，无需检查 token，直接返回 true
		return true;
	}

	/**
     * 判断用户是否想要登入。
     * 检测 header 里面是否包含 Token 字段
	 */
	@Override
	protected boolean isLoginAttempt(ServletRequest request, ServletResponse response) {
		HttpServletRequest req = (HttpServletRequest)request;
		String token = req.getHeader("Token");
		return token != null;
	}

	/**
	 * 执行登录操作
	 */
	@Override
	protected boolean executeLogin(ServletRequest request, ServletResponse response) throws Exception {
		HttpServletRequest httpServletRequest = (HttpServletRequest)request;
		String token = httpServletRequest.getHeader("Token");
		JWTToken jwtToken = new JWTToken(token);
        // 提交给realm进行登入，如果错误他会抛出异常并被捕获
		getSubject(request, response).login(jwtToken);
        // 如果没有抛出异常则代表登入成功，返回true
		return true;
	}
	
	   /**
     * 对跨域提供支持
     */
    @Override
    protected boolean preHandle(ServletRequest request, ServletResponse response) throws Exception {
        HttpServletRequest httpServletRequest = (HttpServletRequest) request;
        HttpServletResponse httpServletResponse = (HttpServletResponse) response;
        httpServletResponse.setHeader("Access-control-Allow-Origin", httpServletRequest.getHeader("Origin"));
        httpServletResponse.setHeader("Access-Control-Allow-Methods", "GET,POST,OPTIONS,PUT,DELETE");
        httpServletResponse.setHeader("Access-Control-Allow-Headers", httpServletRequest.getHeader("Access-Control-Request-Headers"));
        // 跨域时会首先发送一个option请求，这里我们给option请求直接返回正常状态
        if (httpServletRequest.getMethod().equals(RequestMethod.OPTIONS.name())) {
            httpServletResponse.setStatus(HttpStatus.OK.value());
            return false;
        }
        return super.preHandle(request, response);
    }

	/**
	 * @description: 非法请求跳转到/unauthorized/**
	 * @param response
	 * @param message
	 */
	private void responseError(ServletResponse response, String message) {
		HttpServletResponse httpServletResponse = (HttpServletResponse) response;
		try {
			message = URLEncoder.encode(message, "UTF-8");
			httpServletResponse.sendRedirect("/unauthorized/" + message);
		} catch (UnsupportedEncodingException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}
